Web folding apparatus for folding endless webs in a zig-zag manner are known in the art. Such apparatus has included spiral winders at the corners or use of rotating grips that rotate with the folding cylinders to grippers the web, swing it in a radius and then release it in order to impart a fold. Other apparatus has utilized tuckers or swinging and reciprocating arms to impart the zig-zag folds. Some folder apparatus have utilized vacuum and pressure means associated with the folding cylinders to hold the web to the cylinders and to move the web from the cylinders. Thus, for example, in U.S. Pat. No. 940,933 to Klein, apparatus is disclosed which utilizes apertures in rotatable folder cylinders where the apertures alternatively operate in a pressure or vacuum mode to assist in imparting a fold to the web. Other apparatus, for example that disclosed in U.S. Pat. No. 1,186,018 to Meisel and Pat. No. 1,502,333 to Braunstein, have utilized separate vacuum and pressure ports in rotating cylinders to hold the web to the cylinders and to move it therefrom.
Still further, web folding devices have been utilized which use mechanically operated gripper units which are spaced from the rotating folding cylinders to positively grip the web along a fold line and which use vacuum means in the cylinder for transporting the web off the gripper means. Such machines, as also the above-mentioned prior art machines, have been subjected to jam up problems, particularly when operating at fast speeds. It is therefore an object of my invention to provide for a web folding machine which will utilize the advantages of mechanically-operated gripping units to positively grip and hold a web to a web folding cylinder, which may have vacuum means to assist in transporting the web to the gripper means and which at the same time have means allowing rapid operation of the machine without danger of a web jam up.